ANIMALS. 185 
Genus Schizodus, King. / % L/ - 
TELLINITES, Schlotheim. 
AXINUS (OBSCURUS), James Sowerby. 
IsocARDIA (AXINIFORMIS), Phillips. 
CucuLima (ScuLoTHEIM!), Geinitz. 
Donax (suLcata’), J. de C. Sowerby. 
Sepewick1a’ (partim), M‘Coy. 
Diagnosis. — Equivalved: inequilateral, the posterior side being the longest. 
Anterior outline rounded; posterior, tapering towards the extremity. ght valve 
with two smooth cardinal teeth: /e/t valve with three.* The teeth of the left valve 
placed in front of those of the right valve: the central tooth of the former more 
or less bifid, according to species, on its free side, and embraced by both teeth of 
the opposite valve. Palhal line entire. Smooth, or ornamented with fine raised lines 
running parallel to the margins. 
Type Schizodus truncatus, King. 
My-earliest enunciation of this genus was made in the ‘ Annals and Magazine of 
Natural History’ for November 1844, where it is stated, that I proposed instituting 
“© Schizodus for the Permian and Carboniferous Axinuses, to distmguish them from the 
London Clay Awinus ungulatus.”’ An incomplete diagnosis and a tolerably full 
description of it was afterwards inserted in the ‘Geology of Russia,’ vol. 11, pp. 308-9, 
1845, by M. de Verneuil, to whom I had forwarded my MSS. _ I now propose adding 
a few more particulars to what has already been published on the subject. 
The late Mr. James Sowerby, in No. 55 of the ‘Mineral Conchology,’ described a 
new fossil genus under the name of 4wnus, in which he included two widely different 
1 Etym. cx:Zw, I split ; ddovs, a tooth—the typical species having the central tooth of the left valve 
divided on its free side. 
2 This shell is one of the species described by Mr. J. de C. Sowerby in Mr. J. Prestwich’s valuable memoir 
‘On the Geology of the Coal Field of Coalbrook Dale’ (vide Trans. Geol. Soc. Lond., 2d series, vol. v). 
When in London, about 18 months since, Mr. Prestwich kindly allowed me to examine the originals of Mr. 
Sowerby’s species; and I find from my memorandums made at the time, that Donax ? sulcata (op. cit., 
pl. xxxix, fig. 1) is the Isocardia axiniformis of Phillips. Venus ? carbonaria, J. de C. Sow. (op. cit., pl. 
xxxix, fig. 2), is another species of Schizodus ; but as far as I have been able to ascertain, it does not appear 
to have received any other specific name: the same species, occasionally beautifully preserved, occurs in the 
carboniferous shales of Redesdale, Northumberland. 
3 Sedgwickia, which is typified with the S. alternata, M‘Coy, is stated to be “‘entirely without hinge- 
teeth’ (vide Synop. Carb. Fossils, p. 61). Sedgwickia gigantea, M‘Coy, however, appears to be a species of 
Schizodus ;—and the same may be said of Leptodomus fragilis, M‘Coy, Dolabra securiformis, M‘Coy, Mactra 
ovata, M‘Coy, Amphidesma subtruncata, M‘Coy, Anatina deltoida, M‘Coy, Axinus obliques, M‘Coy, &c. 
4 In the original diagnosis published in the ‘Geology of Russia,’ vol. 11, p. 308, it is erroneously stated, 
- through overlooking the small posterior tooth in the left valve'(vide pl. xv, fig. 29 4, e), that each valve is 
furnished with two teeth. : 
5 Annals and Magazine of Natural History, vol. xiv, p. 313. 
Y} 
